Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$172.37	12.847%	$194.5144	$194.51	$194.50	$194.50
Purchase #2	$218.72	9.811%	$240.1786	$240.18	$240.20	$240.20
Purchase #3	$22.50	8.375%	$24.3844	$24.38	$24.40	$24.40
Purchase #4	$166.91	12.351%	$187.5251	$187.53	$187.55	$187.50
Purchase #5	$62.93	6.289%	$66.8877	$66.89	$66.90	$66.90
Purchase #6	$211.61	12.359%	$237.7629	$237.76	$237.75	$237.80
Purchase #7	$91.52	9.112%	$99.8593	$99.86	$99.85	$99.90
7 purchase totals =	$946.56		$1,051.1124	$1,051.11	$1,051.15	$1,051.20